1. Field of Invention
The present invention relates to a hydraulic device in a forge forming technology.
2. Related Art
Referring to “Precision Forging Mould Manual” (Hu Yamin, China Machine Press, Beijing, 2002), an existing three-pin axle and a small-sized cross-axle double closed mould stand are formed of a mould stand and a flexible clamping device. The mould stand includes an up mould plate, an up concave mould seat, an up punch pin, a down mould plate, a down concave mould seat, a down punch pin, and four sets of symmetrically distributed guide columns and guide sleeves. The flexible clamping device includes cylindrical polyurethane rubber, a retaining ring and a connecting bolt, cylinder helical spring, and a stop bolt. The parts and elements are symmetrically distributed in the up mould plate and the down mould plate. During flashless die forging, the cylinder polyurethane rubber and the cylinder helical spring generate a clamping force. After the mould forging is ended, the cylinder helical spring and the cylinder polyurethane rubber push the up concave mould and the down concave mould away from up and down baffles. The advantage is as follows. The mould stand structure is simple and has a low manufacturing cost. However, the polyurethane rubber and the helical spring generate a clamping force which is small and unstable.
A double-closed hydraulic mould stand which can be used for bevel gear and cross-axle flashless cold precision forging at the same time is proposed in Precision forming of aluminum and steel (Hyoji Yoshimuya, Katsuhisa Tanka, Journal of Materials Processing Technology 98 (2000), 196-204), which is formed of a mould stand, and two sets (up and down) of a piston cylinder and a speed ratio mechanism. The advantage is that the clamping force is large, the process application range is wide, and the use of the speed ratio mechanism can enable the up punch pin and the down punch pin to extrude forging at the same speed or different speeds according to process requirements. However, both the up and down cylinders are integral structures, and a bottom shape of the cylinder is complicated, thus causing difficulties in processing and installation. When the annular piston in the up cylinder and the up concave mould seat, the up concave mould bed piece, and the up concave mould ring return upward when the mould forging is ended, the parts fall down completely depending on their own weight. Once being stuck on the up concave mould and the up punch pin, it is very difficult for the cross-axle forging to fall down. The up bearing support and the up hinge base are in a semi arc surface contact, which require difficult processing, so a contact area therebetween is easily decreased, and maintenance is difficult.